TY - JOUR A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Are there two forms of isometric muscle action? BT - Results of the experimental study support a distinction between a holding and a pushing isometric muscle function JF - BMC sports science, medicine & rehabilitation N2 - Background In isometric muscle function, there are subjectively two different modes of performance: one can either hold isometrically – thus resist an impacting force – or push isometrically – therefore work against a stable resistance. The purpose of this study is to investigate whether or not two different isometric muscle actions – the holding vs. pushing one (HIMA vs PIMA) – can be distinguished by objective parameters. Methods Ten subjects performed two different measuring modes at 80% of MVC realized by a special pneumatic system. During HIMA the subject had to resist the defined impacting force of the pneumatic system in an isometric position, whereby the force of the cylinder works in direction of elbow flexion against the subject. During PIMA the subject worked isometrically in direction of elbow extension against a stable position of the system. The signals of pressure, force, acceleration and mechanomyography/-tendography (MMG/MTG) of the elbow extensor (MMGtri/MTGtri) and the abdominal muscle (MMGobl) were recorded and evaluated concerning the duration of maintaining the force level (force endurance) and the characteristics of MMG-/MTG-signals. Statistical group differences comparing HIMA vs. PIMA were estimated using SPSS. Results Significant differences between HIMA and PIMA were especially apparent regarding the force endurance: During HIMA the subjects showed a decisively shorter time of stable isometric position (19 ± 8 s) in comparison with PIMA (41 ± 24 s; p = .005). In addition, during PIMA the longest isometric plateau amounted to 59.4% of the overall duration time of isometric measuring, during HIMA it lasted 31.6% (p = .000). The frequency of MMG/MTG did not show significant differences. The power in the frequency ranges of 8–15 Hz and 10–29 Hz was significantly higher in the MTGtri performing HIMA compared to PIMA (but not for the MMGs). The amplitude of MMG/MTG did not show any significant difference considering the whole measurement. However, looking only at the last 10% of duration time (exhaustion), the MMGtri showed significantly higher amplitudes during PIMA. Conclusion The results suggest that under holding isometric conditions muscles exhaust earlier. That means that there are probably two forms of isometric muscle action. We hypothesize two potential reasons for faster yielding during HIMA: (1) earlier metabolic fatigue of the muscle fibers and (2) the complexity of neural control strategies. KW - Two forms of isometric muscle action KW - Holding isometric muscle action KW - Pushing isometric muscle action KW - Mechanomyography KW - Mechanotendography Y1 - 2017 U6 - https://doi.org/10.1186/s13102-017-0075-z VL - 9 PB - BioMed Central CY - London ER - TY - JOUR A1 - Schaefer, Laura V. A1 - Hoff, Marco A1 - Bittmann, Frank N. T1 - Measuring system and method of determining the Adaptive Force JF - European journal of translational myology N2 - The term Adaptive Force (AF) describes the capability of adaptation of the nerve-muscle-system to externally applied forces during isometric and eccentric muscle action. This ability plays an important role in real life motions as well as in sports. The focus of this paper is on the specific measurement method of this neuromuscular action, which can be seen as innovative. A measuring system based on the use of compressed air was constructed and evaluated for this neuromuscular function. It depends on the physical conditions of the subject, at which force level it deviates from the quasi isometric position and merges into eccentric muscle action. The device enables – in contrast to the isokinetic systems – a measure of strength without forced motion. Evaluation of the scientific quality criteria of the devices was done by measurements regarding the intra- and interrater-, the test-retest-reliability and fatiguing measurements. Comparisons of the pneumatic device with a dynamometer were also done. Looking at the mechanical evaluation, the results show a high level of consistency (r²=0.94 to 0.96). The parallel test reliability delivers a very high and significant correlation (ρ=0.976; p=0.000). Including the biological system, the concordance of three different raters is very high (p=0.001, Cronbachs alpha α=0.987). The test retest with 4 subjects over five weeks speaks for the reliability of the device in showing no statistically significant differences. These evaluations indicate that the scientific evaluation criteria are fulfilled. The specific feature of this system is that an isometric position can be maintained while the externally impacting force rises. Moreover, the device can capture concentric, static and eccentric strength values. Fields of application are performance diagnostics in sports and medicine. KW - Adaptive Force KW - isometric eccentric force KW - muscle action KW - motor control KW - strength measurement system Y1 - 2017 U6 - https://doi.org/10.4081/ejtm.2017.6479 SN - 2037-7460 VL - 27 IS - 3 SP - 152 EP - 159 PB - Unipress CY - Padova ER - TY - GEN A1 - Schaefer, Laura V. A1 - Hoff, Marco A1 - Bittmann, Frank N. T1 - Measuring system and method of determining the Adaptive Force N2 - The term Adaptive Force (AF) describes the capability of adaptation of the nerve-muscle-system to externally applied forces during isometric and eccentric muscle action. This ability plays an important role in real life motions as well as in sports. The focus of this paper is on the specific measurement method of this neuromuscular action, which can be seen as innovative. A measuring system based on the use of compressed air was constructed and evaluated for this neuromuscular function. It depends on the physical conditions of the subject, at which force level it deviates from the quasi isometric position and merges into eccentric muscle action. The device enables – in contrast to the isokinetic systems – a measure of strength without forced motion. Evaluation of the scientific quality criteria of the devices was done by measurements regarding the intra- and interrater-, the test-retest-reliability and fatiguing measurements. Comparisons of the pneumatic device with a dynamometer were also done. Looking at the mechanical evaluation, the results show a high level of consistency (r²=0.94 to 0.96). The parallel test reliability delivers a very high and significant correlation (ρ=0.976; p=0.000). Including the biological system, the concordance of three different raters is very high (p=0.001, Cronbachs alpha α=0.987). The test retest with 4 subjects over five weeks speaks for the reliability of the device in showing no statistically significant differences. These evaluations indicate that the scientific evaluation criteria are fulfilled. The specific feature of this system is that an isometric position can be maintained while the externally impacting force rises. Moreover, the device can capture concentric, static and eccentric strength values. Fields of application are performance diagnostics in sports and medicine. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 346 KW - Adaptive Force KW - isometric eccentric force KW - motor control KW - muscle action KW - strength measurement system Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-402676 ER - TY - GEN A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Are there two forms of isometric muscle action? BT - Results of the experimental study support a distinction between a holding and a pushing isometric muscle function N2 - Background In isometric muscle function, there are subjectively two different modes of performance: one can either hold isometrically – thus resist an impacting force – or push isometrically – therefore work against a stable resistance. The purpose of this study is to investigate whether or not two different isometric muscle actions – the holding vs. pushing one (HIMA vs PIMA) – can be distinguished by objective parameters. Methods Ten subjects performed two different measuring modes at 80% of MVC realized by a special pneumatic system. During HIMA the subject had to resist the defined impacting force of the pneumatic system in an isometric position, whereby the force of the cylinder works in direction of elbow flexion against the subject. During PIMA the subject worked isometrically in direction of elbow extension against a stable position of the system. The signals of pressure, force, acceleration and mechanomyography/-tendography (MMG/MTG) of the elbow extensor (MMGtri/MTGtri) and the abdominal muscle (MMGobl) were recorded and evaluated concerning the duration of maintaining the force level (force endurance) and the characteristics of MMG-/MTG-signals. Statistical group differences comparing HIMA vs. PIMA were estimated using SPSS. Results Significant differences between HIMA and PIMA were especially apparent regarding the force endurance: During HIMA the subjects showed a decisively shorter time of stable isometric position (19 ± 8 s) in comparison with PIMA (41 ± 24 s; p = .005). In addition, during PIMA the longest isometric plateau amounted to 59.4% of the overall duration time of isometric measuring, during HIMA it lasted 31.6% (p = .000). The frequency of MMG/MTG did not show significant differences. The power in the frequency ranges of 8–15 Hz and 10–29 Hz was significantly higher in the MTGtri performing HIMA compared to PIMA (but not for the MMGs). The amplitude of MMG/MTG did not show any significant difference considering the whole measurement. However, looking only at the last 10% of duration time (exhaustion), the MMGtri showed significantly higher amplitudes during PIMA. Conclusion The results suggest that under holding isometric conditions muscles exhaust earlier. That means that there are probably two forms of isometric muscle action. We hypothesize two potential reasons for faster yielding during HIMA: (1) earlier metabolic fatigue of the muscle fibers and (2) the complexity of neural control strategies. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 344 KW - Holding isometric muscle action KW - Mechanomyography KW - Mechanotendography KW - Pushing isometric muscle action KW - Two forms of isometric muscle action Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-402084 ER - TY - GEN A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Muscular Pre-Activation Can Boost the Maximal Explosive Eccentric Adaptive Force T2 - Postprints der Universität Potsdam Humanwissenschaftliche Reihe N2 - The improvement of power is an objective in training of athletes. In order to detect effective methods of exercise, basic research is required regarding the mechanisms of muscular activity. The purpose of this study is to investigate whether or not a muscular pre-activation prior to an external impulse-like force impact has an effect on the maximal explosive eccentric Adaptive Force (xpAFeccmax). This power capability combines different probable power enhancing mechanisms. To measure the xpAFeccmax an innovative pneumatic device was used. During measuring, the subject tries to hold an isometric position as long as possible. In the moment in which the subjects’ maximal isometric holding strength is exceeded, it merges into eccentric muscle action. This process is very close to motions in sports, where an adaptation of the neuromuscular system is required, e.g., force impacts caused by uneven surfaces during skiing. For investigating the effect of pre-activation on the xpAFeccmax of the quadriceps femoris muscle, n = 20 subjects had to pass three different pre-activation levels in a randomized order (level 1: 0.4 bar, level 2: 0.8 bar, level 3: 1.2 bar). After adjusting the standardized pre-pressure by pushing against the interface, an impulse-like load impacted on the distal tibia of the subject. During this, the xpAFeccmax was detected. The maximal voluntary isometric contraction (MVIC) was also measured. The torque values of the xpAFeccmax were compared with regard to the pre-activation levels. The results show a significant positive relation between the pre-activation of the quadriceps femoris muscle and the xpAFeccmax (male: p = 0.000, η2= 0.683; female: p = 0.000, η2= 0.907). The average percentage increase of torque amounted +28.15 ± 25.4% between MVIC and xpAFeccmax with pre-pressure level 1, +12.09 ± 7.9% for the xpAFeccmax comparing pre-pressure levels 1 vs. 2 and +2.98 ± 4.2% comparing levels 2 and 3. A higher but not maximal muscular activation prior to a fast impacting eccentric load seems to produce an immediate increase of force outcome. Different possible physiological explanatory approaches and the use as a potential training method are discussed. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 582 KW - Adaptive Force KW - neuromuscular pre-activation KW - power improvement KW - muscular activity KW - adaptation to external force impact Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439189 SN - 1866-8364 IS - 582 ER - TY - GEN A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Coherent behavior of neuromuscular oscillations between isometrically interacting subjects BT - experimental study utilizing wavelet coherence analysis of mechanomyographic and mechanotendographic signals T2 - Postprints der Universität Potsdam : Humanwissenschaftliche Reihe N2 - Previous research has shown that electrical muscle activity is able to synchronize between muscles of one subject. The ability to synchronize the mechanical muscle oscillations measured by Mechanomyography (MMG) is not described sufficiently. Likewise, the behavior of myofascial oscillations was not considered yet during muscular interaction of two human subjects. The purpose of this study is to investigate the myofascial oscillations intra- and interpersonally. For this the mechanical muscle oscillations of the triceps and the abdominal external oblique muscles were measured by MMG and the triceps tendon was measured by mechanotendography (MTG) during isometric interaction of two subjects (n = 20) performed at 80% of the MVC using their arm extensors. The coherence of MMG/MTG-signals was analyzed with coherence wavelet transform and was compared with randomly matched signal pairs. Each signal pairing shows significant coherent behavior. Averagely, the coherent phases of n = 485 real pairings last over 82 ± 39 % of the total duration time of the isometric interaction. Coherent phases of randomly matched signal pairs take 21 ± 12 % of the total duration time (n = 39). The difference between real vs. randomly matched pairs is significant (U = 113.0, p = 0.000, r = 0.73). The results show that the neuromuscular system seems to be able to synchronize to another neuromuscular system during muscular interaction and generate a coherent behavior of the mechanical muscular oscillations. Potential explanatory approaches are discussed. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 480 KW - motor unit synchronization KW - muscle KW - task KW - contractions KW - humans KW - magnetoencephalography KW - systems KW - power KW - hand KW - time Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-419864 IS - 480 ER - TY - JOUR A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Coherent behavior of neuromuscular oscillations between isometrically interacting subjects BT - experimental study utilizing wavelet coherence analysis of mechanomyographic and mechanotendographic signals JF - Scientific Reports N2 - Previous research has shown that electrical muscle activity is able to synchronize between muscles of one subject. The ability to synchronize the mechanical muscle oscillations measured by Mechanomyography (MMG) is not described sufficiently. Likewise, the behavior of myofascial oscillations was not considered yet during muscular interaction of two human subjects. The purpose of this study is to investigate the myofascial oscillations intra- and interpersonally. For this the mechanical muscle oscillations of the triceps and the abdominal external oblique muscles were measured by MMG and the triceps tendon was measured by mechanotendography (MTG) during isometric interaction of two subjects (n = 20) performed at 80% of the MVC using their arm extensors. The coherence of MMG/MTG-signals was analyzed with coherence wavelet transform and was compared with randomly matched signal pairs. Each signal pairing shows significant coherent behavior. Averagely, the coherent phases of n = 485 real pairings last over 82 ± 39 % of the total duration time of the isometric interaction. Coherent phases of randomly matched signal pairs take 21 ± 12 % of the total duration time (n = 39). The difference between real vs. randomly matched pairs is significant (U = 113.0, p = 0.000, r = 0.73). The results show that the neuromuscular system seems to be able to synchronize to another neuromuscular system during muscular interaction and generate a coherent behavior of the mechanical muscular oscillations. Potential explanatory approaches are discussed. KW - motor unit synchronization KW - muscle KW - task KW - contractions KW - humans KW - magnetoencephalography KW - systems KW - power KW - hand KW - time Y1 - 2018 U6 - https://doi.org/10.1038/s41598-018-33579-5 SN - 2045-2322 VL - 8 SP - 1 EP - 10 PB - Macmillan Publishers Limited CY - London ER - TY - JOUR A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Muscular Pre-Activation Can Boost the Maximal Explosive Eccentric Adaptive Force JF - Frontiers in Physiology N2 - The improvement of power is an objective in training of athletes. In order to detect effective methods of exercise, basic research is required regarding the mechanisms of muscular activity. The purpose of this study is to investigate whether or not a muscular pre-activation prior to an external impulse-like force impact has an effect on the maximal explosive eccentric Adaptive Force (xpAFeccmax). This power capability combines different probable power enhancing mechanisms. To measure the xpAFeccmax an innovative pneumatic device was used. During measuring, the subject tries to hold an isometric position as long as possible. In the moment in which the subjects’ maximal isometric holding strength is exceeded, it merges into eccentric muscle action. This process is very close to motions in sports, where an adaptation of the neuromuscular system is required, e.g., force impacts caused by uneven surfaces during skiing. For investigating the effect of pre-activation on the xpAFeccmax of the quadriceps femoris muscle, n = 20 subjects had to pass three different pre-activation levels in a randomized order (level 1: 0.4 bar, level 2: 0.8 bar, level 3: 1.2 bar). After adjusting the standardized pre-pressure by pushing against the interface, an impulse-like load impacted on the distal tibia of the subject. During this, the xpAFeccmax was detected. The maximal voluntary isometric contraction (MVIC) was also measured. The torque values of the xpAFeccmax were compared with regard to the pre-activation levels. The results show a significant positive relation between the pre-activation of the quadriceps femoris muscle and the xpAFeccmax (male: p = 0.000, η2= 0.683; female: p = 0.000, η2= 0.907). The average percentage increase of torque amounted +28.15 ± 25.4% between MVIC and xpAFeccmax with pre-pressure level 1, +12.09 ± 7.9% for the xpAFeccmax comparing pre-pressure levels 1 vs. 2 and +2.98 ± 4.2% comparing levels 2 and 3. A higher but not maximal muscular activation prior to a fast impacting eccentric load seems to produce an immediate increase of force outcome. Different possible physiological explanatory approaches and the use as a potential training method are discussed. KW - Adaptive Force KW - neuromuscular pre-activation KW - power improvement KW - muscular activity KW - adaptation to external force impact Y1 - 2019 U6 - https://doi.org/10.3389/fphys.2019.00910 SN - 1664-042X VL - 10 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Parkinson patients without tremor show changed patterns of mechanical muscle oscillations during a specific bilateral motor task compared to controls JF - Scientific Reports N2 - The pathophysiology of Parkinson’s disease (PD) is still not understood. There are investigations which show a changed oscillatory behaviour of brain circuits or changes in variability of, e.g., gait parameters in PD. The aim of this study was to investigate whether or not the motor output differs between PD patients and healthy controls. Thereby, patients without tremor are investigated in the medication off state performing a special bilateral isometric motor task. The force and accelerations (ACC) were recorded as well as the Mechanomyography (MMG) of the biceps brachii, the brachioradialis and of the pectoralis major muscles using piezoelectric-sensors during the bilateral motor task at 60% of the maximal isometric contraction. The frequency, a specific power ratio, the amplitude variation and the slope of amplitudes were analysed. The results indicate that the oscillatory behaviour of motor output in PD patients without tremor deviates from controls: thereby, the 95%-confidence-intervals of power ratio and of amplitude variation of all signals are disjoint between PD and controls and show significant differences in group comparisons (power ratio: p = 0.000–0.004, r = 0.441–0.579; amplitude variation: p = 0.000–0.001, r = 0.37–0.67). The mean frequency shows a significant difference for ACC (p = 0.009, r = 0.43), but not for MMG. It remains open, whether this muscular output reflects changes of brain circuits and whether the results are reproducible and specific for PD. Y1 - 2020 U6 - https://doi.org/10.1038/s41598-020-57766-5 SN - 2045-2322 VL - 10 PB - Macmillan Publishers Limited, part of Springer Nature CY - London ER - TY - GEN A1 - Schaefer, Laura V. A1 - Bittmann, Frank N. T1 - Parkinson patients without tremor show changed patterns of mechanical muscle oscillations during a specific bilateral motor task compared to controls T2 - Postprints der Universität Potsdam : Humanwissenschaftliche Reihe N2 - The pathophysiology of Parkinson’s disease (PD) is still not understood. There are investigations which show a changed oscillatory behaviour of brain circuits or changes in variability of, e.g., gait parameters in PD. The aim of this study was to investigate whether or not the motor output differs between PD patients and healthy controls. Thereby, patients without tremor are investigated in the medication off state performing a special bilateral isometric motor task. The force and accelerations (ACC) were recorded as well as the Mechanomyography (MMG) of the biceps brachii, the brachioradialis and of the pectoralis major muscles using piezoelectric-sensors during the bilateral motor task at 60% of the maximal isometric contraction. The frequency, a specific power ratio, the amplitude variation and the slope of amplitudes were analysed. The results indicate that the oscillatory behaviour of motor output in PD patients without tremor deviates from controls: thereby, the 95%-confidence-intervals of power ratio and of amplitude variation of all signals are disjoint between PD and controls and show significant differences in group comparisons (power ratio: p = 0.000–0.004, r = 0.441–0.579; amplitude variation: p = 0.000–0.001, r = 0.37–0.67). The mean frequency shows a significant difference for ACC (p = 0.009, r = 0.43), but not for MMG. It remains open, whether this muscular output reflects changes of brain circuits and whether the results are reproducible and specific for PD. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 602 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-445431 SN - 1866-8364 IS - 602 ER -